Howdy!

...
It's a good idea to turn off 'die_on_bad_params' in HTML::Template - in
case this plugin tries to put in the parameters and they're not
available in your template.
Here's a quick TT example:
...

Howdy!

[% FOREACH CAP_Messages %]

[% message %]

[% END %]
...
If you use TT, I recommend using CAP-TT and a more recent version
(0.09), which supports cgiapp's load_tmpl hook and then this plugin will
automatically supply TT with the relevant messages. Your runmode could
be this simple:
sub start {
my $self = shift;
my $session = $self->session;
return $self->tt_process( 'output.tt' );
}
I don't have the experience to weigh in on how you'd do this with other
templates (HTDot, Petal), but basically, this plugin will put in a loop
parameter called 'CAP_Messages'. Within each element of that loop,
you'll have two tags, 'classification' and 'message'.
NOTE: I have broken backwards compatibility with this release (0.30) and
the loop parameter's default name is now 'CAP_Messages'. If you used the
old __CAP_Messages or want to use another name, feel free to use the
capms_config to override the "-loop_param_name".
DESCRIPTION
This plugin by default needs a session object to tuck away the
message(s). It's recommended that you use this in conjunction with
CGI::Application::Plugin::Session. You can opt to not have the messages
persist and thereby, not use CAP-Session by using the
"-dont_use_session" option in the "capms_config" method.
This plugin hooks into cgiapp's load_tmpl method and if you've pushed
any messages in the stack, will automatically add the message
parameters.
In the functions, there are scope & classification keys and when they're
used for either display or your API purposes (clearing, pop'ing, etc),
the classification is an exclusive specification. Meaning, if you ask
for messages with the 'ERROR' classification, it will only deal with
messages that you've pushed in with the 'ERROR' classification. Any
messages that have no classification aren't included.
The scope key is not exclusive, meaning that if you ask for messages
with a 'mainpage' scope, it will deal with messages that you've pushed
with that scope as well as any messages that you've pushed in without a
scope.
If you use both scope & classification, it blends both of those rules,
first getting all matching messages with the same classification and
then filtering out messages that are scoped and don't match the scope
you're looking for.
This logic may change as I get feedback from more saavy developers. What
we may end up doing is have a plugin configuration where you can dictate
the logic that's used.
FUNCTIONS
push_message
$self->push_message(
-scope => 'mainpage',
-message => 'Your listing has been updated',
-classification => 'INFO',
);
You provide a hash to the push_message() method with three possible
keys:
* message - a text message. You can put HTML in there - just make sure
you don't use the ESCAPE=HTML in your HTML::Template code
* scope - which runmode(s) can this message appear? If you want to
specify just one, use a scalar assignment. Otherwise, use an array
reference with the list of runmodes.
* classification - a simple scalar name representing the classification
of your message (i.e. 'ERROR', 'WARNING' ... ). This is very useful for
CSS styles (see template example above).
The scope & classification keys are optional. If you don't provide a
scope, it will assume a global presence.
messages
my @messages = $self->messages();
my @messages = $self->messages( -scope => 'mainpage' );
my @messages = $self->messages( -scope => 'mainpage', -classification => 'ERROR' );
my @messages = $self->messages( -classification => 'ERROR' );
If you want to take a gander at the message stack data structure, you
can use this method.
Optionally, you can use a hash parameters to get a slice of the
messages, using the same keys as specified in the push_message() method.
It will return an array reference of the matching messages or 'undef',
if there's either no messages in the stack or no messages that match
your specification(s).
pop_message
my $message = $self->pop_message();
my $message = $self->pop_message( -scope => 'mainpage' );
my $message = $self->pop_message( -scope => 'mainpage', -classification => 'WARNING' );
my $message = $self->pop_message( -classification => 'ERROR' );
Pops off the last message from the stack and returns it. Note that this
just returns the -message part.
You can pop off an exact message, given a hash parameters, using the
same keys as specified in the push_message() method.
Otherwise, it will pop off the message, given the current runmode and
the last message added.
clear_messages
$self->clear_messages();
$self->clear_messages( -scope => 'mainpage' );
$self->clear_messages( -scope => 'mainpage', -classification => 'ERROR' );
$self->clear_messages( -classification => 'ERROR' );
Clears the message stack.
Optionally, you can clear particular slices of the message stack, given
a hash parameters, using the same keys as specified in the
push_message() method.
If you specify a scope, it will clear any messages that are either
global or match that scope
If you specify a classification, it will clear any messages that have
that classification (but not any messages that don't have any
classification).
If you specify both, it will combine both that logic in an AND fashion.
capms_config
$self->capms_config(
-automatic_clearing => 1,
-dont_use_session => 1,
-loop_param_name => 'MyOwnLoopName',
-message_param_name => 'MyOwnMessageName',
-classification_param_name => 'MyOwnClassificationName',
);
There is a configuration option that you, as the developer can specify:
* -automatic_clearing: By default, this is turned off. If you override
it with a true value, it will call clear_messages() automatically after
the messages are automatically put into template.
* -dont_use_session: This will override this Plugin's dependence on
CGI::Application::Plugin::Session and instead, temporarily store the
message data such that it will be available to templates within the same
web request, but no further. If you're running your cgiapp under a
persistent state (mod_perl), we'll also make sure your messages are gone
by the end of the request.
* -loop_param_name: This will override the default __CAP_Messages (or
CAP_Messages for TT users) name for the loop of messages, which is only
used for the "load_tmpl" callback. Meaning, this configuration will only
impact your template code. So if you use the 'MyOwnLoopName' above, then
your template code (for HTML::Template users) should look like:
...
* -message_param_name: This will override the default '-message' in both
the template code as well as the keys in each hashref of the arrayref
that's returned by the messages() function. So a call to messages() may
return:
[ { 'MyOwnMessageName' => 'this is just a test' }, ... ]
instead of:
[ { '-message' => 'this is just a test' }, ... ]
Likewise, your templates will need to use your parameter name:
Here's the message:
* -classification_param_name: Just like the "-message_param_name"
parameter - this will override the default '-classification' key in both
the template code as well as the keys in each hashref of the arrayref
that's returned by the messages() function. So a call to messages() may
return:
[ { 'MyOwnClassificationName' => 'ERROR', 'MyOwnMessageName' => 'this is just a test' }, ... ]
instead of:
[ { '-classification' => 'ERROR', '-message' => 'this is just a test' }, ... ]
Likewise, your templates will need to use your parameter name:

">
Here's the message:

AUTHOR
Jason Purdy, ""
SEE ALSO
CGI::Application and CGI::Application::Plugin::Session
BUGS
Please report any bugs or feature requests to
"bug-cgi-application-plugin-messagestack@rt.cpan.org", or through the
web interface at
. I will be notified, and then you'll automatically be
notified of progress on your bug as I make changes.
I suspect that this code could use some expert guidance. I hacked it
together and I'd hate to think that it would be responsible for slowing
templates down. Please feel free to submit patches, guiding comments,
etc.
ACKNOWLEDGEMENTS
Thanks to the guys on the #cgiapp channel
COPYRIGHT & LICENSE
Copyright 2005 Jason Purdy, all rights reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.